if the high speed mixture screw has vibrated out on a polaris 700cc ski will this cause a lean mixture to melt a piston?

Did you notice the ski running real rough prior to leaning out? It should have gone real rich as the screw backed out causing it to run poorly.

i wasnt actually riding the ski myself and the guy that was has no idea mechanically
he was going full throttle&the screw is completely missing out of the hole